The Plain Man's Guide to Aerosols

HOW AEROSOLS ARE FILLED

	An aerosol is made up of several basic components: An aerosol can The product The propellant A valve with dip tube An actuator A dust cap (not shown) These all have to be assembled, and this is achieved using automatic filling machinery which can operate at speeds in excess of 400 cans per minute.
For conventional aerosols the key steps in the filling process are:-
	1. Start with an empty aerosol container.  This will be made of tinplate or aluminium, or perhaps glass. The capacity of the container will be greater than that which is declared on the pack.  (See section on propellants for an explanation)
	2. The product, usually in the form of a liquid, is now added. This contains all the active ingredients, except for the propellant. The volume of liquid is very carefully controlled to ensure that it conforms with Weights & Measures legislation.
	3. The Aerosol valve is now fitted (crimped) to the can.  This is a very critical operation and the crimping machinery has to be carefully set up to ensure that the can / valve seal does not leak. Where a 'small' actuator is to be used, this will be fitted on to the valve before it is crimped onto the can.
	The propellant is now injected under pressure, through the valve. The propellant may be in the form of a liquified gas, or a compressed gas. If a liquified gas is used it will exist as both a liquid, and vapour in the aerosol can head space.  The volume of liquid in the can will increase, as shown in this example. If a compressed gas is used, it will usually only be in the head space, above the liquid in the can, and there will be little or no increase in liquid volume. Again, the volume of liquid is very carefully controlled to ensure that it conforms with Weights & Measures legislation.
The aerosol is now in a pressurised state due to the addition of the propellant.  The cans are now immersed in a water bath at 50°C to check for any leaks.  Any cans that leak are rejected.
	If a large, or special, actuator is required it is fitted now.  Where necessary, a dust cap is also fitted. Finally the can will be date / batch coded, and shrink wrapped or boxed as required.

Home ~|~ History ~|~ Safety ~|~ Filling ~|~ Propellants ~|~ Aerosol Cans ~|~ Aerosol Valves
How an Aerosol Works ~|~ Links to other Aerosol and Associated Sites